San Diego (/ˌsæn diˈeɪɡoʊ/ SAN dee-AY-goh, Spanish: [san ˈdjeɣo]; Spanish for 'Saint Didacus') is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States and the seat of San Diego County, the fifth most populous county in the United States, with 3,338,330 estimated residents as of 2019. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center. San Diego is the second largest city in the state of California, after Los Angeles.
Wudu District, under the jurisdiction of Longnan City, Gansu Province, is located in the southeast of Gansu Province, the central part of Longnan City and the middle reaches of the Bailong River. Wudu began as a place name in the pre-Qin Dynasty, Wudu County in the Western Han Dynasty, Jiizhou in the Tang Dynasty, Wudu County in the Republic of China, and the county was withdrawn in 2004. Wudu District is the political, economic, cultural, transportation center and military center of Longnan, and one of the regional central cities in the southeast of Longnan. It has jurisdiction over 4 subdistrict offices, 26 towns, 8 townships, 2 ethnic townships, 50 communities and 649 villages, covering an area of 4683 square kilometers; the total population is 602829, the resident population is 568100, and the urbanization rate is 40.56% (2017). Wudu District is located in the junction of Qin and Ba Mountains, known as "Ba Shu throat, Qin long lock key". It is the friend of Gansu, Shaanxi and Sichuan provinces.